15.3% efficiency all-small-molecule organic solar cells enabled by symmetric phenyl substitution

Abstract

Synergistic optimization of donor-acceptor blend morphologyis a hurdle in the path of realizing efficient non-fullerene small-molecule organic solar cells (NFSM-OSCs) due to the anisotropic conjugated backbones of both donor and acceptor. Therefore, developing a facile molecular design strategy to effectively regulate the crystalline properties of photoactive materials, and thus, enable the optimization of blend morphology is of vital importance. In this study, a new donor molecule B1, comprising phenyl-substituted benzodithiophene (BDT) central unit, exhibits strong interaction with the non-fullerene acceptor BO-4Cl in comparison with its corresponding thiophene-substituted BDT-based material, BTR. As a result, the B1 is affected and induced from an edgeon to a face-on orientation by the acceptor, while the BTR and the acceptor behave individually for the similar molecular orientation in pristine and blend films according to grazing incidence wide angle X-ray scattering results. It means the donor-acceptor blend morphology is synergistically optimized in the B1 system, and the B1:BO-4Cl-based devices achieve an outstanding power conversion efficiency (PCE) of 15.3%, further certified to be 15.1% by the National Institute of Metrology, China. Our results demonstrate a simple and effective strategy to improve the crystalline properties of the donor molecule as well as synergistically optimize the morphology of the all-small-molecule system, leading to the high-performance NFSM-OSCs.

A Review of Grazing Incidence Small‐ and Wide‐Angle X‐Ray Scattering Techniques for Exploring the Film Morphology of Organic Solar Cells

“…Hou and coworkers studied the effect of SVA on all small molecule OSCs (B1:BO‐4Cl and benzodithiophene terthiophene rhodanine (BTR):BO‐4Cl). [ 76 ] Solvent‐annealed B1:BO‐4Cl blend film showed an improved donor and acceptor crystallinity, as well as a dominant face‐on orientation. The face‐on ratio was 94% in the blend film, whereas it was only 2% in the pristine B1 film.…”

Moving Alkyl‐Chain Branching Point Induced a Hierarchical Morphology for Efficient All‐Small‐Molecule Organic Solar Cells

“…Gaining from cooperation of the novel donor: acceptor (D:A) material synthesis and device fabrication, tremendous strides have been achieved on the power conversion efficiencies (PCEs) of organic solar cells (OSCs). [ 1–9 ] In non‐fullerene systems, significant PCEs were usually obtained based on polymer donors due to the polymers have a stronger ability to form an interpenetrating networks in bulk‐heterojunctions (BHJ) for charge carrier transport in comparison with small molecular donors. [ 10–15 ] Compared with polymers, small molecular donors have advantages of high purity and definite molecular structures.…”

“…[ 25–27 ] Therefore, tuning the morphology of the active layer is one of the most critical factors which need to be considered for the performance improvement for ASM‐OSCs. [ 7,22,28–30 ] For matching with the small molecular acceptors such as Y6, we reported a small molecular donor ZR1 based on dithieno[2,3‐d:2ʹ,3ʹ‐dʹ]benzo[1,2‐b:4,5‐bʹ]dithiophene (DTBDT) unit. Binary all‐small‐molecule OSC based on ZR1:Y6 blend achieved the highest efficiency of 14.34% by optimizing their hierarchical morphologies, in which the donor or acceptor rich domains with size up to ca.…”

Diketopyrrolopyrrole linked porphyrin dimers for visible-near-infrared photoresponsive nonfullerene organic solar cells

“…8,23,24 However, SM donors sporadically succeeded with several advantages such as high crystallinity, rapid aggregation pathways, controllable energy levels, etc., and as a result, assisting the significant enhancement of PCEs in recent years. [25][26][27][28][29][30][31][32][33][34][35][36][37][38] However, the combination of a SM donor and a SM acceptor has been a bottleneck hindering the performance so far due to their high crystallinity and unfavourable phase separation and morphologies. 25,39 Recently, Wei et al reported an A-p-D-p-A structural narrow bandgap SM donor based on a larger coplanar core DTBDT and achieved the highest PCE of 14.34% at that time for binary all SM OSCs by optimizing their hierarchical morphologies.…”